Human whole blood is made up of several different components, including red blood cells, white blood cells and platelets. These blood components are suspended in plasma, the liquid medium component of blood. As used herein, the term “component” includes plasma.
Whole blood collected from healthy donors is routinely separated into its components, and one or more of the separated components are used for later administration (transfusion) to a patient who may be in need of the particular component. For example, red blood cells may be administered to a patient to replace blood loss or to treat patients with chronic anemia. Plasma may be administered to treat clotting factor deficiencies. Platelets are commonly administered as a therapy to cancer patients whose ability to generate platelets has been compromised by chemotherapy.
Blood components can be separated and collected by so called “manual” methods or by “apheresis.” For example, in a manual system for collecting platelets, whole blood is withdrawn from a donor and then separated (by, for example, centrifugation) into platelets (suspended in plasma) and red blood cells. The separated platelets are collected and typically stored until administration to the patient. The collected platelets from several “random” donors are often pooled to provide a single therapeutic dose for a patient. A “therapeutic dose” of platelets (i.e., the number of platelets transfused to a patient in a single transfusion) is generally understood to mean anywhere between 2.0–4.0×1011 and, more typically, approximately 3×1011 platelets. The term “therapeutic dose,” as used herein, however, is not limited to the above-identified number of platelets, but includes any number of platelets that may be administered to a patient as part of a therapy.
Platelets (as well as other blood components) can also be collected by “apheresis.” In apheresis, whole blood is withdrawn from a donor and passed through a disposable fluid circuit that includes a phlebotomy needle for insertion into the donor, tubing and interconnected containers. The fluid circuit is associated with a separation device. The withdrawn whole blood is introduced into the separation device where it is separated into its desired components. In platelet apheresis, the separated platelets are collected in the separation device and/or pre-attached collection containers.
During a platelet apheresis procedure, the donor remains “connected” to the device, and red cells and some plasma are returned to the donor. Return of the other components such as red cells and plasma provides for a continuous process and allows a greater volume of blood to be processed. As a result, in a platelet apheresis procedure, unlike a manual collection, a therapeutic dose of about 3×1011 platelets can be collected from a single donor. Such platelets are sometimes referred to as “single donor platelets.” In fact, some of today's apheresis systems also allow for collection of a “double dose” or even a “triple dose” of single donor platelets.
Red blood cells have traditionally been collected by manual methods. More recently, however, systems and methods have been developed to allow for the collection of red blood cells by apheresis. Whether collected manually or by apheresis, the red cells are separated from platelets and plasma, collected and usually stored until later administration to a patient.
There are several commercially available apheresis systems. One of the earliest and still widely used systems is the CS3000® Blood Cell Separator available from Baxter Healthcare Corporation of Deerfield, Ill. Baxter Healthcare Corporation also makes and sells the Amicus® Separator. Both the CS3000® and Amicus® are used in the collection of platelets and plasma. The Alyx™ device, also made by Baxter Healthcare Corporation, is a portable apheresis device adapted for the collection of red blood cells as well as other blood components. The Alyx™ device is generally described in U.S. Pat. No. 6,294,094, which is incorporated herein by reference.
Other apheresis systems, such as the COBE Spectra and COBE Trima are available from COBE Laboratories, Inc. (a division of Gambro) of Arvada, Colo. Fresenius AG, of Bad Homburg, Germany, sells apheresis systems under the product designations AS-104 and the AS.TEC-204. Haemonetics Corporation of Braintree, Mass., sells a device under the name MCS Plus. All of the above apheresis systems are believed to be capable of providing at least one therapeutic dose of about 3×1011 platelets suspended in plasma. At least some of the above-described apheresis systems may also be adapted to collect red blood cells.
Whether collected manually or by apheresis, before transfusion to a patient, the collected blood component may be subjected to an additional treatment to ensure the safety of the blood component (e.g., platelets, plasma, red blood cells) intended for transfusion. Specifically, the collected blood components are treated to remove or otherwise inactivate virus and/or bacteria (“pathogens”) which may reside in the particular blood component. Many of the pathogen inactivation methods involve combining the platelets with a chemical compound which acts directly on the pathogen, or adding a photoactivation compound which, when stimulated by light, acts on the pathogen.
These pathogen inactivation methods have been developed to provide a blood product that is substantially free of pathogens. These methods are subject to government regulatory review and approval. By way of example, a method for the inactivation of pathogens in red blood cells is described in U.S. Pat. No. 6,093,725, which is incorporated herein by reference. A method for the inactivation of pathogens in platelets and plasma is described in U.S. patent application Ser. No. 09/325,325, filed Jun. 3, 1999, also incorporated by reference herein. That method utilizes a photoactivated psoralen compound that is added to blood platelets and/or blood plasma. The platelets with psoralen compound are contacted with light of a specific wavelength (e.g., UV-A) to activate the psoralen compound and, consequently, inactivate pathogens present in the blood product. In this method for pathogen inactivation using psoralen photoactivation compounds, the collected platelets (in plasma) are combined with a specific quantity of a synthetic storage medium. The relative quantities and/or ratio of synthetic storage medium and plasma in which the platelets are suspended are selected to enhance the efficacy of the pathogen inactivation method, as well as to maintain the viability of the platelets during storage, and prior to transfusion.
In the above-described platelet pathogen inactivation method, the ratio of synthetic storage medium and plasma provides an environment that enhances the activation of the photochemical compound and results in increased viral and bacterial kill. The synthetic storage medium (with plasma) also provides and/or helps maintain favorable physiologic conditions, such as pH, buffering and sources of nutrients which are conducive to effecting pathogen inactivation and/or to sustaining platelet metabolism and viability during extended storage.
Unfortunately, not all apheresis procedures and systems currently used result in a (pathogen inactivation) treatment-ready blood product. For example, in the context of platelet collection, not all apheresis procedures result in a platelet product that includes a therapeutic or otherwise acceptable dose of platelets that is suspended in a suitable synthetic medium and in the desired relative quantities and/or ratio of synthetic medium and plasma. Thus, in order to treat the collected platelets in an established platelet pathogen inactivation procedure, one may first have to “convert” such platelets to obtain a “treatment-ready” platelet product. Likewise, in the context of other blood products (e.g., red blood cells) it may also be necessary to “convert” the collected blood component to one that is suitable for treatment in established methods of pathogen inactivation of the given blood component.
Thus, it would be desirable to provide a method and system to allow for easy preparation of such treatment-ready blood products, regardless of the method used to collect the source blood component. The resulting “converted” product is one that is (1) suitable for treatment using established pathogen inactivation protocols, (2) suitable for extended storage, if necessary, and, (3) suitable for transfusion to a patient.